Investigation of a magnetic tunnel junction based sensor for the detection of defects in reinforced concrete at high lift-off

Muhamad Arif Ihsan Mohd Noor Sam, Zhenhu Jin, Mikihiko Oogane, Yasuo Ando

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Magnetic flux leakage (MFL) testing is a method of non-destructive testing (NDT), whereby the material is magnetized, and when a defect is present, the magnetic flux lines break out of the material. The magnitude of the leaked magnetic flux decreases as the lift-off (distance from the material) increases. Therefore, for detection at high lift-off, a sensitive magnetic sensor is required. To increase the output sensitivity, this paper proposes the application of magnetic tunnel junction (MTJ) sensors in a bridge circuit for the NDT of reinforced concrete at high lift-off. MTJ sensors were connected to a full-bridge circuit, where one side of the arm has two MTJ sensors connected in series, and the other contains a resistor and a variable resistor. Their responses towards a bias magnetic field were measured, and, based on the results, the sensor circuit sensitivity was 0.135 mV/mT. Finally, a reinforced concrete specimen with a 1 cm gap in the center was detected. The sensor module (with an amplifier and low pass filter circuits) could determine the gap even at 50 cm, suggesting that MTJ sensors have the potential to detect defects at high lift-off values and have a promising future in the field of NDT.

Original languageEnglish
Article number4718
JournalSensors (Switzerland)
Issue number21
Publication statusPublished - 2019 Nov 1


  • Lift-off
  • Magnetic tunnel junction sensors
  • Non-destructive testing
  • Reinforced concrete

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Electrical and Electronic Engineering


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